>But back to my original question? Is T-Rex possible...from a materials
>"strenght to weight ratio" assuming it was composed of calcium bones...and
>similar muscels, ligaments etc. as are present day critters?
Yes. Elephants push the limit of elephant construction, just as any animal
gently pushes the limit of it's construction. Waste does poorly in natural
selection. If elephants had a larger portion of their mass in bone, they
could be much larger - but at their present size that would be a waste, so
they don't have it.
>If not...then what are the fossils?
>
>If so....then why not similarly large critters now?
Well, there are some - in the sea. Whales are by far the largest creatures
every to have lived.
At present we really don't know much about the advantages and disadvantages of
size. Some of the Eocene mammals were far larger than an elephant. Since
the Eocene, I think mammoths have been as big as they get. This is just one
of those situations where we know a fact but cannot explain it. It happens.